1. Field of the Invention
The present invention relates to a method of manufacturing an ink jet print head in which an ink ejecting print element and a support member capable of supplying ink to the print element are bonded together with adhesive. The invention also relates to such an ink jet print head.
2. Description of the Related Art
An example of currently available ink jet print head has a construction as shown in FIG. 8, in which a support member 100 and a chip-like print element substrate 300 are bonded together with an adhesive 400 (see FIG. 9). The print element substrate 300 is bonded to areas surrounding ink supply ports 101 in the support member 100. The print element substrate 300 has a plurality of ejection openings formed therein to eject ink supplied from the ink supply ports 101 of the support member 100. The print element substrate 300 also has an electrothermal conversion element (heater) or a piezoelectric element to create an ink ejection energy.
As shown in FIG. 9, the adhesive 400 applied to the areas surrounding the ink supply ports 101 of the support member 100 is pressed by, and spreads over the back of, the print element substrate 300 as the print element substrate 300 is bonded to the support member 100. FIG. 9 is an enlarged cross section of FIG. 8, showing a bonded portion between the print element substrate 300 and the areas surrounding the ink supply ports 101 of the support member 100. FIG. 9 corresponds to a cross section of the print element substrate 300 taken along the line IX-IX of FIG. 8 and a cross section of the areas surrounding the ink supply ports 101 taken along the line IX-IX of FIG. 8. Designated 101A is a surface of the support member 100 in which the ink supply ports 101 are formed. Denoted 301 is a surface of the print element substrate 300 in which ink introducing ports 301 are formed. S0 indicates a squeezed-out portion of the adhesive 400.
When the amount of the squeezed-out portion S0 of the adhesive 400 becomes large, a possibility increases that communication portions between the ink supply ports 101 and the ink introducing ports 301 may be narrowed. The communication portions, when narrowed, may cause quality degradation of printed images due to possible ink ejection failures, leading to a deteriorated yield of print head production. It is therefore necessary to control the amount of squeezed-out portion of the adhesive 400.
As a method for controlling the amount of squeezed-out portion of the adhesive 400, Japanese Patent Laid-Open Nos. 2001-162802 and 2001-47620 proposed a method of absorbing an excess amount of the adhesive 400 into a groove formed in a bonding surface.
To reduce the manufacturing cost of the ink jet print head, there is a growing need in recent years to make the print element substrate 300, the most expensive component in the print head, as small as possible.
FIG. 10A is a cross section of the existing print element substrate 300 of a relatively large size, taken along the line IX-IX of FIG. 8. FIG. 10B is a cross section of the print element substrate 300 of a smaller size, taken along the line IX-IX of FIG. 8. FIG. 10C is a cross section, taken along the line IX-IX of FIG. 8, of those areas of the support member 100 which surround the ink supply ports 101, the support member 100 corresponding to the large size print element substrate 300 of FIG. 10A, FIG. 10D is a cross section, taken along the line IX-IX of FIG. 8, of those areas of the support member 100 which surround the ink supply ports 101, the support member 100 corresponding to the small size print element substrate 300 of FIG. 10B. The print element substrate 300 of this example has three ink introducing ports 301 formed therein, to which three different kinds of inks having different colors or the like can be supplied from the three ink supply ports 101 of the support member 100. The print element substrate 300 is formed with three sets of ejection opening arrays (300A, 300B, and 300C), one for each of the three different inks. The pitch 40 between the three ink introducing ports 301 of the print element substrate 300 matches the pitch between the three ink supply ports 101 of the support member 100. The pitch 400 is hereinafter referred to also as an “inter-color pitch”. The width X of the ink introducing ports 301 matches the width of the ink supply ports 101.
As the print element substrate 300 is reduced in size, the inter-color pitch 40 of the print element substrate 300 also decreases as shown in FIG. 10B. At the same time, the inter-color pitch 40 of the support member 100 also decreases as shown in FIG. 10D. The reduction in the inter-color pitch 40 causes the widths X of the ink supply ports 101 and the ink introducing ports 301 to shrink. Since these widths X are required to smoothly supply ink to the print element substrate 300, it is necessary to secure an appropriate size for the width X to ensure precise ink ejections and thereby maintain a high print quality.
In the existing print element substrate 300, a sufficient width X can be secured even if the adhesive 400 is squeezed out into the inside of the ink supply ports 101 and the ink introducing ports 301 by an amount S, as shown in FIG. 11A. So, if the adhesive 400 is squeezed out to some extent, there is little possibility of the communication portions between the ink supply ports 101 and the ink introducing ports 301 being narrowed to such a degree as will degrade the print quality.
However, in the case of the small size print element substrate 300, since the width is narrow, a sufficient width X is difficult to secure when the adhesive 400 is squeezed out by an amount S, as shown in FIG. 11B. So, even if the squeeze-out amount of the adhesive 400 is relatively small, the ink paths between the ink supply ports 101 and the ink introducing ports 301 are likely to be narrowed to a degree that could affect the print quality.
As a measure to solve this problem, a conceivable method may be to have an excess amount of the adhesive 400 absorbed into a groove, as proposed in Japanese Patent Laid-Open Nos. 2001-162802 and 2001-47620. However, when the print element substrate 300 is smaller as in the case of FIG. 11B, it is difficult to secure enough space to form the groove in order to prevent the adhesive 400 from being squeezed out into the ink path.
Another possible method may involve reducing the amount of adhesive 400 applied to the areas surrounding the ink supply ports 101 so as to reduce the squeezed-out volume of the adhesive 400. However, the amount of adhesive 400 to be applied needs to be determined by considering the surface precision of an ink supply port forming surface 101A and an ink introducing port forming surface 301A, the height of the adhesive 400 applied, and precision variations of a print head assembly machine. Therefore, to reduce the amount of adhesive 400 requires increasing the surface precision of the ink supply port forming surface 101A and the ink introducing port forming surface 301A, reducing the height of the adhesive 400 applied, and increasing the precision of the assembly machine, which in turn results in an increase in cost.